1. Field of the Invention
This invention relates to automated embroidery operations. More specifically, the present invention relates to an embroidery hoop and the bracket for mounting an embroidery hoop on the hoop guide of an embroidery machine.
2. Description of the Prior Art
Embroidery commonly enhances the decorative appearance of a wide range of items. Typically, the embroidering is imparted on a workpiece by automated embroidery machines. The workpiece is mounted on any number of hoops, each hoop in turn being mounted on an automatically controlled hoop guide, also known as the X-Y driver, of an embroidery machine. The hoop guide moves the hoop relative to the needle of the embroidery machine as the needle introduces stitching to the workpiece. To ensure an accurate embroidery design, especially during mass production, the hoop must attach securely and precisely to the hoop guide. Unfortunately, repeated mounting and removing of the hoop wears the hoop attachment bracket, degrading the resolution of the stitching imparted on the fabric. For this reason, there is a need for an embroidery hoop attachment bracket which provides for secure and precise mounting of the embroidery hoop to the automatically controlled hoop guide of an embroidery machine by reducing wear on the hoop attachment bracket.
U.S. Pat. No. 5,291,843, issued Mar. 8, 1994, to Masayaki Hori, describes an attachment structure, shown in FIGS. 1 and 2, for detachably attaching an embroidery hoop to the automatically controlled hoop guide of an embroidery machine. A hoop 10 for holding a workpiece and hoop attachment bracket 12 are shown in FIG. 1. A hoop guide bracket 14 designed to matingly receive the hoop attachment bracket 12 is seen in FIG. 2. The hoop guide attachment bracket 14 is mounted to an automatically controlled hoop guide (not shown). The '843 attachment structure, including both the hoop attachment bracket 12 and the hoop guide attachment bracket 14, removably attaches the hoop 10 to the hoop guide such that the hoop can be moved by the hoop guide in a horizontal plane in synchronism with the reciprocating motion of the sewing needle of a sewing machine (not shown).
When the hoop attachment bracket 12 is removably attached to the hoop guide-attachment bracket 14, each of the two engagement pins 16 extending from the hoop attachment bracket 12 is closely received in a tight friction fit by a corresponding U-shaped slot 18 in the upturned flange portion 33 of the hoop guide attachment bracket 14. A spring clip 24 of the hoop guide attachment bracket 14 is articulated back such that the projection member 20 of the hoop attachment bracket 12 clears a knuckle portion 22 of the spring member 24. Once the hoop 10 is seated, the spring member 24 is released, biasing the projection member 20 and the hoop 10 downwardly. The spring member 24 and the engagement pins 16 act to maintain the hoop 10 stationary relative to the hoop guide.
During large-scale embroidery operations, thousands of hoops 10 are mounted and dismounted from the hoop guide. Unfortunately, repeated embroidery hoop installation results in excessive wear on the engagement pins 16 and their respective slots 18. As the engagement pins 16 and their respective slots 18 wear, the slots 18 no longer receive the engagement pins 16 in a tight friction fit as play develops between the engagement pins 16 and their respective slots 18. The resultant play causes the hoop 10 to move or wobble relative to the hoop guide, thereby dramatically effecting the resolution of the embroidery designs imparted on the workpiece. As a result, manufacturers must repair or replace hoops 10 or hoop attachment brackets 12 often.
Several other types of embroidery hoop attachment brackets are described in the patent literature. For example, U.S. Pat. No. 4,411,208, issued Oct. 25, 1983, to Koji Nishida et al., describes an embroidery frame for automatic embroidery machine. The apparatus includes a frame with a horizontal tang for an attachment. The tang is received in a slot in the machine and secured by threaded fasteners threadingly clamping the tang therein.
U.S. Pat. No. 5,101,746, issued Apr. 17, 1992, to Ricky J. Frye, describes a work holder for sewing machines. The device includes a frame with an attachment including two parallel posts extending outwardly, each having an annular groove distally disposed. Each post is received in a cylindrical bore of the machine. Radial, cylindrical chambers extend from the bores. Spring-loaded balls in the chambers are biased toward the bore and engage with the groove when the posts are inserted therein.
U.S. Pat. No. 5,261,340, issued Nov. 16, 1993, to Ralph F. Conley, Jr. et al., describes a detachable template clamp having a removable sewing template. The apparatus includes a template with an attachment including two parallel throughbores. The machine has an adaptor which traps the frame adaptor against guide rails. The machine adaptor has two posts extending toward the guide rails that are received in the frame adaptor throughbores.
U.S. Pat. No. 5,353,725, issued Oct. 11, 1994, to Hisato Sakakibara, describes front and rear embroidery frame mounting members. The apparatus includes a front and a rear attachment. The machine has a rear attachment including a flattened, C-shaped member having a vertically disposed slot. The frame has a horizontal flange with a vertical pin extending therefrom that is received by the machine attachment. The machine has a front attachment including a vertical pin. The frame has an attachment including a horizontal flange having a vertical throughbore for receiving the vertical pin.
Japanese Patent No. 1,033,262, published Feb. 3, 1989, issued to Aisin Seiki KK, in the abstract describes a machine including a fixed magnet. The frame includes a metal plate. The frame may be selectably fixed to the machine by magnetic adhesion. A problem encountered with the '262 machine is that the magnet can be easily dislodged if the frame is bumped during embroidery. Also, when heavier objects are embroidered, the frame tends to disengage from the machine.
None of the above references, taken alone or in combination, are seen as teaching or suggesting the presently claimed embroidery hoop attachment assembly.